Aging is characterized by an altered stress response that underlies a compromised resistance to disease or injury. Activation of inflammatory and coagulant pathways is a frequent consequence of severe critical illnesses and results in the progression of systemic inflammatory response syndrome (SIRS). Recent evidence suggests that adipose tissue-derived signaling proteins, including cytokines, coagulation factors and hormones, may play an important role in the inflammatory response. Our long-term goals are to identify the mechanisms by which adipose tissue contributes to age-dependent severity of SIRS and to develop therapeutic strategies for decreasing vulnerability to critical illnesses in the aged. For these studies we will use two widely accepted mouse models of SIRS - acute endotoxemia induced by injection with bacterial endotoxin lipopolysaccharide and an intra-abdominal sepsis model induced by cecal ligation and puncture. The objective of this project is to identify and evaluate the expression of adipose-derived inflammatory and coagulant factors that differ by aging upon inflammatory stress. Our central hypothesis is that expression patterns of inflammatory / coagulant factors in the adipose tissue during SIRS are significantly altered by aging and that this alteration contributes to age-dependent severity of critical illnesses. To achieve the above goals, we will pursue the following three specific aims: (1) To define the role of adipose tissue in age-related alterations of coagulation during critical illness. (2) To understand the mechanisms of age-related inflammatory cytokine production in the adipose tissue during critical illness. (3) To evaluate methods of body fat loss as potential therapies and preventative measures for reducing severity of critical illness in the aged. These studies will provide significant insight into the association of the previously neglected adipose organ in aging and critical illness.